The St. George Rotunda is the oldest standing building in Sofia, built in the fourth century by the Romans.
The red brick early Christian rotunda was built on the site of a pagan temple. It has since been used as a mosque, at which point the famous murals inside were painted over (they have been revealed during restoration work since). The red brick theme continues inside the entrance, creating a somber atmosphere.
Walking around the back, we admired the ruins of a Roman street, Basilica and small buildings from the ancient town of Serdica.
Although we only stumbled across this ancient church by chance as we were passing en route to the airport, it's definitely a must-see for anyone visiting Sofia.